(Cat? OR feline) AND NOT dog?
Cat? W/5 behavior
(Cat? OR feline) AND traits
Cat AND charact*

This guide provides a more detailed description of the syntax that is supported along with examples.

This search box also supports the look-up of an IP.com Digital Signature (also referred to as Fingerprint); enter the 72-, 48-, or 32-character code to retrieve details of the associated file or submission.

Concept Search - What can I type?

For a concept search, you can enter phrases, sentences, or full paragraphs in English. For example, copy and paste the abstract of a patent application or paragraphs from an article.

Concept search eliminates the need for complex Boolean syntax to inform retrieval. Our Semantic Gist engine uses advanced cognitive semantic analysis to extract the meaning of data. This reduces the chances of missing valuable information, that may result from traditional keyword searching.

Publishing Venue

Related People

Abstract

The present method provides a technique for etching silicon nitride which eliminates the need for hot etchants, such as hot hydrophosphoric acid or NH(4)H(2)PO(4).

Country

United States

Language

English (United States)

This text was extracted from a PDF file.

At least one non-text object (such as an image or picture) has been suppressed.

This is the abbreviated version, containing approximately
91% of the total text.

Page 1 of 2

Etching Silicon Nitride With Buffered Hydrofluoric Acid

The present method provides a technique for etching silicon nitride which
eliminates the need for hot etchants, such as hot hydrophosphoric acid or
NH(4)H(2)PO(4).

Because of the relative inertness of silicon nitride film, it requires such hot
etchants. While it was known that silicon nitride films were etchable by
concentrated hydrofluoric acid (49%), this etchant had not been used because it
appeared to attack the photoresist usually utilized for masks during etching.

The following procedure avoids the above problems by the utilization of
buffered hydrofluoric acid as the etchant.

With reference to Fig. 1, silicon nitride film 10 covers substrate 11. Heavily
doped phosphosilicate glass film 12 covers the silicon nitride film. Then, Fig. 2, a
thin layer of pyrolytic silicon dioxide is deposited on the phosphosilicate glass.
Then, utilizing standard photo-resist 13 and etchants for silicon dioxide and
phosphosilicate glass, the pattern shown in Fig. 2 is formed. This is the negative
of the pattern which is to be etched in the silicon nitride.

The wafer is then heated to a temperature of about 1200 degrees C. At this
temperature, the following reaction takes place in the shaded area 14 beneath
the silicon nitride in Fig. 3: 3Si(3)N(4) + 2P(2)O(5) 4SiP + 5SiO(2) + 6N(2).

The wafer is then dip etched in buffered hydrofluoric acid, during which the
remaining silicon dioxide, phosphosilicate glass, and the conver...